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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 127 records · Page 7
All sourcesNASA NTRSDOE OSTI
DOE OSTI2022

Controlling Pinhole Radius and Areal Density in a-Si/SiOx Using Metal-Assisted Chemical Etching

Polysilicon on silicon oxide (poly-Si/SiOx) passivating contacts with predominant charge-carrier transport via pinholes are currently prepared via a>1000 degrees C thermal step to induce oxide break-up. Herein, we develop the precursor of a pinhole-enabled poly-Si/SiOx contact utilizing room temperature metal-assisted chemical etching (MACE) to form pinholes in the SiOx. The pinholes were created via electroless Ag nanoparticle (Ag NP) deposition followed by the MACE of intrinsic amorphous hydrogenated silicon (a-Si:H) on SiOx, creating isolated mesopores through the film stack. By varying the MACE etching solution (HF:H2O2) concentration, we were able to vary the pinhole areal density over four orders of magnitude (104-107 cm-2). We observed the Ostwald ripening of the Ag NP to enable control over the pinhole radii. Our work demonstrates proof-of-concept for a-Si:H/SiOx with mesopores across the film stack, which may serve as precursor for the development of poly-Si/SiOx passivating contacts of both polarities.

MATERIALS SCIENCE,SOLAR ENERGY↗
DOE OSTI2025

Physical patterning of high-Q superconducting niobium resonators via ion beam etching

The development of superconducting quantum circuits increasingly involves the exploration of chemically distinct materials and complex multilayered structures. Accelerating this trend may benefit from low-damage, materials-agnostic patterning techniques that are compatible with a broad range of materials. Here, in this work, we investigate the utility of low-energy ion beam etching (IBE), a physical patterning technique, as an alternative to reactive ion etching for fabricating low-loss superconducting resonators. We use niobium (Nb) resonators as a test platform, leveraging their well-characterized performance metrics for benchmarking. To address IBE-induced surface redeposition, we introduce an in situ aluminum capping layer combined with targeted post-fabrication chemical treatment. This strategy yields resonators with internal quality factors as high as 6 × 10 5 in the single-photon regime at 50 mK. These results establish low-energy IBE as a promising patterning technique for superconducting devices, with the potential to accelerate development across chemically diverse and multilayered material platforms.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2024

Wet-Etching of Acoustically Spalled GaAs for Substrate Reuse

Acoustic spalling is a promising technique for substrate reuse in the fabrication of gallium arsenide (GaAs) photovoltaic cells. However, the acoustic spalling process can leave the substrate with areas of rough surface morphology that can interfere with subsequent cell growth and processing. In this work, we investigate the use of wet etchants to smooth the surface of acoustically spalled GaAs substrates. We evaluated six different etchants. Of those tested, an 8:1:1 mixture of sulfuric acid, hydrogen peroxide, and water at 30 degrees C and a moderate stirring rate showed the greatest roughness reduction per mass loss while producing the desired morphology. This etchant was then applied to an acoustically spalled 2-inch GaAs wafer. A single-junction GaAs cell was then grown via metalorganic vapor-phase epitaxy on this substrate, an acoustic spalled substrate without a smoothing etch, and an epi-ready substrate. Use of the 8:1:1 H2SO4:H2O2:H2O etchant produced cells an average efficiency of 12.8% as compared to that of 2.0% grown on the unetched acoustically spalled substrate and 16.3% grown on the epi-ready substrate. The results of this work demonstrate that wet etching is a viable method for smoothing the surface of spalled GaAs substrates, paving the way for substrate reuse via acoustic spalling at efficiencies that approach growth on epi-ready substrates.

etching↗
DOE OSTI2021

Characterization of CdZnTeSe Nuclear Detector Chemically Etched in Bromine Methanol

Semiconductor nuclear radiation detectors made from tertiary and quaternary compounds of cadmium telluride (CdTe) can operate at room temperature without cryogenic cooling. One of such materials that have become of great interest is cadmium zinc telluride selenide (CdZnTeSe). Compared to other CdTe-based materials, such as cadmium zinc telluride (CdZnTe), CdZnTeSe can be grown with much less Te inclusions and sub-grain boundary networks. Chemical etching is often used to smoothen wafer surfaces during detector fabrication. This paper presents the characterization of CdZnTeSe that is chemically etched using bromine methanol solution. Infrared imaging shows that the wafer has no sub-grain boundary networks that often limit detector performance. The current-voltage (I-V) characterization experiment gave a resistivity of 4.6 × 10 10 Ω-cm for the sample. The I-V curve was linear in the ±10 to ±50 volts range. An energy resolution of 7.2% was recorded at 100 V for the 59.6-keV gamma line of 241 Am.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2022

Atomic Layer Deposition of Ruthenium Films Using Ruthenium Diketonates and O 2 , H 2 , or N 2 O: The Role of Ruthenium Etching

In this work, the evolution of the surface during the steps that comprise the atomic layer deposition (ALD) of ruthenium films on a nickel substrate using tris(2,2,6,6-tetramethyl-3,5-heptanedionato)ruthenium(III) (Ru(tmhd) 3 ) and molecular oxygen was characterized using a combination of X-ray photoelectron (XPS) and reflection–absorption infrared (RAIRS) spectroscopies. The uptake of the Ru metalorganic precursor was determined to be activated, involving the average loss of two out of the three ligands (and the retention of the third, in molecular form, at the surface–vacuum interface), and self-limited, as required in ALD. The reaction of the resulting layer from that first half of the ALD cycle with O 2 proved to be more complex: in addition to the desired removal of the carbon-containing material, the Ni substrate becomes oxidized, and some Ru is etched away in the form of the volatile RuO 4 gas. By testing different combinations of exposures and temperatures it was determined that Ru film growth was possible, but tuning and optimizing the ALD or atomic layer etching (ALE) process conditions for maximum film growth or removal rate per cycle proved difficult. Replacing O 2 with H 2 was shown not to be viable either, as such an agent can reduce the nickel oxide formed after O 2 treatments (in fact, Ru(tmhd) 3 can do this as well) but not remove the carbonaceous material deposited on the surface by the Ru precursor. The use of N 2 O, on the other hand, showed much promise, being capable of removing most of the surface carbon without affecting the Ru film or the Ni substrate.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2025

Depolymerization as a Design Strategy: Depolymerization Etching of Polymerization-Induced Microphase Separations

Thermally triggered depolymerization has traditionally been viewed through the lens of sustainability and recycling, not as a constructive tool for materials design. Herein, we show that selective, thermally triggered depolymerization to gaseous monomer serves as a solvent-free strategy for generating porosity in nanostructured polymer materials, offering a means to bypass the mass transport limitations inherent in conventional solution-based etching. As a demonstration platform, we employed polymerization-induced microphase separation (PIMS) to generate disordered bicontinuous block copolymer structures with embedded depolymerizable domains. By incorporating a methacrylate block susceptible to thermal depolymerization within a cross-linked, depolymerization-resistant styrenic matrix, we developed a process we term depolymerization etching of polymerization-induced microphase separations (DEPIMS). This approach enables highly selective and efficient domain removal via reversion to monomer to produce mesoporous materials with high surface areas (>200 m 2 /g). Subsequent surface functionalization yielded mesoporous adsorbents with tunable uptake kinetics and among the highest dye adsorption capacities reported for PIMS-derived materials, demonstrating the adaptability of the DEPIMS platform for chemical separations. DEPIMS can also be extended to a gram-scale, one-pot approach to yield mesoporous materials with recoverable monomer in under 12 h. These findings reposition thermal depolymerization from a sustainability tool to a broadly enabling strategy for scalable, on-demand fabrication of functional nanostructured materials.

Depolymerization↗
DOE OSTI2021

Investigations of the stability of etched or platinized p-InP(100) photocathodes for solar-driven hydrogen evolution in acidic or alkaline aqueous electrolytes

Here, the stability of p-InP photocathodes performing the hydrogen-evolution reaction (HER) has been evaluated in contact with either 1.0 M H 2 SO 4 (aq) or 1.0 M KOH(aq), with a focus on identifying corrosion mechanisms. Stability for the solar-driven HER was evaluated using p-InP electrodes that were either etched or coated with an electrodeposited Pt catalyst (p-InP/Pt). Variables such as trace O 2 were systematically controlled during the measurements. Changes in surface characteristics after exposure to electrochemical conditions as well as electrode dissolution processes were monitored using X-ray photoelectron spectroscopy (XPS) and inductively coupled plasma mass spectrometry (ICP-MS). In either H 2 SO 4 or KOH, etched p-InP photoelectrodes corroded cathodically under illumination, forming metallic In 0 at the electrode surface. In contrast, electrodeposition of Pt kinetically stabilized illuminated p-InP photocathodes in both H 2 SO 4 and KOH by inhibiting the cathodic corrosion pathway. Notably, when held at 0 V vs. the reversible hydrogen electrode (RHE) in 1.0 M H 2 SO 4 (aq), p-InP/Pt exhibited a stable current density (J) of ~–18 mA cm –2 for >285 h under simulated 1 Sun illumination. The long-term current density vs. potential (J–E) behavior at pH 0 and pH 14 of p-InP/Pt photocathodes correlated with changes in the surface chemistry as well as the dissolution of p-InP. In acidic media, the J–E behavior of p-InP/Pt photocathodes remained nearly constant with time, but the surface of a p-InP/Pt electrodes gradually turned P-rich via a slow and continuous leaching of In ions. In alkaline electrolyte, the surface of p-InP/Pt electrodes was passivated by formation of an InO x layer that exhibited negligible dissolution but led to a substantial degradation in the J–E characteristics. Consequently, changes in the catalytic kinetics and surface stoichiometry are both important considerations for determining the corrosion chemistry and the long-term operational stability of InP photoelectrodes.

14 SOLAR ENERGY↗
DOE OSTI2024

A transient site balance model for atomic layer etching

We present a transient site balance model of plasma-assisted atomic layer etching of silicon (Si) with alternating exposure to chlorine gas (Cl 2 ) and argon ions (Ar + ). Molecular dynamics (MD) simulation results are used to provide parameters for the model. The model couples the dynamics of a top monolayer surface region ('top layer') and a perfectly mixed subsurface region ('mixed layer'). The differential equations describing the rates of change of the Cl coverage in the two layers are transient mass balances. Model predictions include Cl coverages and rates of etching of various species from the surface as a function of Cl 2 or Ar + fluence. The simplified phenomenological model reproduces the MD simulation results well over a range of conditions. Comparing model predictions directly to experimental optical emission spectroscopy data, as reported in a previous paper, provides further evidence of the accuracy of the model.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2022

Etched Silicon Planar CRL Optics for the High-Energy X-ray Diffraction Beamlines 11-ID-B and 11-ID-C at the APS

We report the focusing of high-energy X-rays is most commonly achieved by commercially available compound refractive lenses (CRL), which are added together in larger structures. There is a need for high-energy X-ray beamlines to enable focusing in only one dimension down to a few micrometers to study layered materials and thin films. High-energy X-rays above 50 keV require often 100 lenses or more, therefore it is more efficient to etch the complete arrays of lenses into a monolithic substrate like a silicon wafer. Custom lens arrays were fabricated for the high-energy x-ray beamlines 11-ID-B, and 11-ID-C at the Argonne National Laboratory. The fabrication required tuning parameters of the Bosch process to optimize the etching of deep vertical sidewalls at a reasonable speed without overheating. The beamline 11-ID-B is equipped with lens arrays of 85-110 lenses for 59 keV and 190-250 lenses for 87 keV photon energy, focusing the beam vertically below 5.0 µm at the sample positions between 1600 mm to 2100 mm. 11-ID-C has received arrays of 435 lenses that focus 106 keV X-rays to a vertical height of 2.0 µm at the sample position. In both cases, the flux density gain in the focal spot is larger than a factor of 20, relative to using slits to cut the beam size. The lens setup is permanently installed and can be moved in and out of the beam during the experiment without further alignment. The lenses have enabled operando diffraction studies on interfaces in batteries and the development of pair distribution function (PDF) analysis using grazing incidence geometry.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2021

Erosion of focus rings in capacitively coupled plasma etching reactors

In plasma etching reactors, the structure surrounding the wafer, often called a focus ring (FR), plays an important role in maintaining uniform fluxes of reactants across the wafer. The FR is typically made of dielectric materials. During the plasma etching process, the sheath that forms over the wafer to accelerate ions anisotropically into the surface extends over the FR. Electrical charging of the FR modifies the sheath relative to that over the wafer. On the one hand, one wants the sheath to be uniform across the wafer-FR boundary to enable uniform fluxes to the edge of the wafer. On the other hand, maintaining a high voltage sheath over the FR will erode the FR, which is undesirable as the FR is a consumable component that must be periodically replaced in high volume manufacturing. In this work, we computationally investigated the consequences of dielectric constant ε of the FR materials on erosion of the FR. The series capacitance of the FR and its underlying structure is typically smaller than that of the wafer and its underlying structure. As a result, the FR charges quickly relative to the wafer, which then reduces the voltage across the sheath on top of the FR. The ion energy and angular distributions (IEADs) striking the FR are, therefore, generally lower in energy with a broader angular distribution. With ε = 2, the ion energies striking the middle to the outer edge of the FR are 30–180 eV, whereas for ε = 100, the ion energies are 120–380 eV. At the transition between the wafer and the FR, there is a skew in the IEAD as large as 15° that results from the difference in sheath thickness above the wafer and the FR. This skew and the erosion rate across the FR are functions of the dielectric constant of the FR material. With low ε, the FR charges quickly, less plasma is produced above the FR, and there is less voltage across the sheath that results in less FR erosion. Increasing ε of the FR produces a higher sheath voltage as well as higher ion fluxes over the FR, which increases erosion, while the skew at the edge of the wafer is less severe. Further, the material of the subsurface portion of the FR, which dominates its capacitance, is an important consideration in the design of the substrate assembly.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Integrated Electrochemical Decontamination and Etching System

Researchers at Los Alamos have developed a novel electrochemical technology consisting of several components in a system that provides a self-contained, efficient, semi- or fully automated, and flexible decontamination system for metals and metal alloys. Any number of novel system configurations are possible such as: 1) a recirculating bath to clean contaminated parts, 2) a recirculating solution through a suction head for larger parts or surfaces, and 3)injecting and removing the solution in/out of large containment tanks. The System is integrated with a proprietary contactor for separation of radioactive components. The decontamination system can also be used to etch steel alloys for increased adhesion of coatings. Coatings embedded with nanoparticles have also been developed and tested on these etched surfaces. We are seeking input from potential users or interested parties regarding the development of the technology.

42 ENGINEERING↗
DOE OSTI2020

Metal-Assisted Chemical Etching and Electroless Deposition for Fabrication of Hard X-ray Pd/Si Zone Plates

Zone plates are diffractive optics commonly used in X-ray microscopes. Here, we present a wet-chemical approach for fabricating high aspect ratio Pd/Si zone plate optics aimed at the hard X-ray regime. A Si zone plate mold is fabricated via metal-assisted chemical etching (MACE) and further metalized with Pd via electroless deposition (ELD). MACE results in vertical Si zones with high aspect ratios. The observed MACE rate with our zone plate design is 700 nm/min. The ELD metallization yields a Pd density of 10.7 g/cm 3 , a value slightly lower than the theoretical density of 12 g/cm 3 . Fabricated zone plates have a grid design, 1:1 line-to-space-ratio, 30 nm outermost zone width, and an aspect ratio of 30:1. At 9 keV X-ray energy, the zone plate device shows a first order diffraction efficiency of 1.9%, measured at the MAX IV NanoMAX beamline. With this work, the possibility is opened to fabricate X-ray zone plates with low-cost etching and metallization methods.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Effects of Plasma Etching on Dopant Compensation between p- and n-Type Poly-Si Fingers in Passivated Interdigitated Back Contact Solar Cells

Efficiencies surpassing 26% have been achieved for single-junction Si solar cells based on the interdigitated back contact (IBC) architecture. However, the possibility of lateral shunting between the doped fingers has limited industrial adoption thus far. To avoid this possibility of shunt, complicated patterning techniques of the doped rear fingers have been developed, but spreading can still occur through multiple pathways during cell processing. Patterning can be simplified by using masked plasma-enhanced chemical vapor deposition (PECVD), but spreading during deposition will also lead to contamination of the isolation region between doped fingers. We significantly reduce the effect of this spreading through a short, gentle plasma etching step, which enables a trap-assisted compensation mechanism to take effect more easily than without the plasma etch. These two effects combined allow for the use of a simple patterning technique while still maintaining a highly resistive region between the doped fingers, and will reduce the complexity of IBC cell fabrication overall.

atom probe↗
DOE OSTI2021

Metal-based passivation-assisted plasma etching of III-v semiconductors

According to one embodiment, a method includes performing a plasma etching process on a masked III-V semiconductor, and forming a passivation layer on etched portions of the III-V semiconductor. The passivation layer includes at least one of a group III element and/or a metal from the following: Ni, Cr, W, Mo, Pt, Pd, Mg, Ti, Zr, Hf, Y, Ta, and Sc.

Harrison, Sara Elizabeth↗
DOE OSTI2023

Etching of water-sensitive optics with water-in-oil emulsions

In one inventive concept, a method for etching an optic includes obtaining a microemulsion, where the microemulsion includes a continuous oil phase, a surfactant system comprising at least one surfactant, and water, submerging at least a portion of the optic in the microemulsion, and agitating by ultrasonication the microemulsion for etching the optic submerged therein.

Baxamusa, Salmaan H.↗